The present embodiments relate to a novel process for passivating polymeric particles to prevent undesirable interaction with the environment. In specific embodiments, the passivation prevents the interaction between binder polymer resin in toner particles and the epoxy embedding resin which causes artifacts observed in transmission electron microscopy (TEM) imaging of the toner particles. However, the present embodiments are intended to be used to passivate any polymeric surface.
Development of high performance marking materials requires an understanding of the morphology and nanostructure of the various components within such materials, including colorants and specialty additives. For example, the microstructure of composite particles, as well as the location and distribution of the constituent materials within the binder polymer resin, affects their performance. Transmission electron microscopy is commonly used for accurately determining the primary particle dimensions, morphology and distribution of constituents that comprise the internal structure of marking materials such as toners. To obtain a “picture” depicting the internal composition of marking materials, which are typically smaller than 10 microns in diameter, requires that such particles be initially embedded in a curable resin and subsequently cut into thin slices for TEM analysis. Good candidates for an embedding resin must perform the following: (1) encapsulate but not permeate the particles, (2) cure at room temperature, and (3) be suitable for cross-sectioning and withstand electron beam irradiation without significant loss of mass.
Undesirable artifacts, however, can be seen in the TEM imaging process. For example, a possible artifact can, and often does, arise from an interaction between epoxy embedding resin and polyester particles that are being analyzed. The specific interaction investigated is thought to occur between the epoxy and crystalline polyester present in the particles. This interaction was altering the nature of the crystalline polyester in the toner particles being studied and would often lead to incorrect interpretations of toner morphology. Several embedding resins have been tested but epoxy has been the only one to work satisfactorily as an embedding resin. As such, passivation of the surface of the particles is required to obtain accurate images when embedding the particles in epoxy resin.
Thus, there is a need to devise a technique for passivating polymeric surfaces, such as for example, those of the particles, when it is necessary to render those surfaces such that they will not undergo any undesirable interactions with the environment. In specific situations, there is a need to devise such techniques to passivate polymeric particles to facilitate the embedding of particles, such as toner particles, containing crystalline polyester into epoxy resin while preventing unwanted artifacts.